This invention relates to certain improvements in single use syringes both with and without aspirating mechanisms.
These improvements relate to improvements over certain prior structures which are the subject of prior patents, these being identified as U.S. Pat. No. 5,531,691, entitled Single Use Syringe Assembly, issued Jul. 2, 1996; U.S. Pat. No. 5,562,623, entitled Single Use Syringe Assembly Including Spring Clip Lock and Plunger; and, U.S. Pat. No. 6,283,941, entitled Single Use Syringe With Aspirating Mechanism. The contents of these prior patents are incorporated herein by reference.
These prior patents describe certain improvements relating to the single use syringes both with and without aspirating mechanisms. In the course of working with these syringe structures, certain improvements have been discovered and are the subject of this present application. These are more clearly described in the present specification and associated drawings, and are briefly summarized.
The prior art syringes generally have a front nose piece which is shown and described in the prior art as being cylindrical. It has been discovered that by providing an X-shaped nose piece for the front portion of the syringe, improvements in the operation, manufacturing and functioning of the syringe are achieved. The X-shaped front nose piece permits better centering of the needle on the front of the syringe, easier securement of the cover of the needle after use (to reduce needle “sticks”), and provides easier assembly of the nose piece to the barrel of the syringe because of the use of the arms of the X-shaped nose piece during assembly.
Further, the '941 patent shows and describes a spring locking clip about the plunger, employed as described in that patent. Certain improvements have been made to that spring locking clip making it more effective to manufacture, less expensive and more efficient and secure in its use for the purposes intended in the syringe. These will be described in further detail, but overall there is an improvement in the operation achieved with the changes to the spring lock clip described herein.
Another improvement with respect to the prior art is the ability to ensure that the spring clip is attached at a specific location on the plunger to guarantee that the amount of medicament loading in the barrel of the syringe is always precisely predetermined, i.e., a preset amount, such as 1 cc or 0.5 cc, as appropriate. This is achieved by ensuring that the clip is located at and on a precise and exact ratchet tooth each time the clip is attached to the plunger. As a further aspect of this invention, the clip is provided with a tab which cooperates with a notch in the specific ratchet tooth location so that when the clip is attached to the ratchet, the tab sets in the notch, and if sought to be mechanically attached at any other location, it will not properly set in place because there will be no corresponding notch. This will ensure that the clip is precisely located where desired on the plunger to control the exact amount of dosage loaded into the syringe.